1. Field of the Invention
The present invention relates to a light quantity adjustment apparatus that is incorporated into an image pickup apparatus such as a video camera and still camera or a projection apparatus such as a projector and that adjusts a quantity of light such as a shooting light quantity and projection light quantity.
2. Description of the Prior Art
Generally, this type of light quantity adjustment apparatus is known as an apparatus in which a substrate having an optical-axis aperture in a shooting light path (or projection light path) is disposed, a plurality of light quantity adjustment blades is disposed in the substrate to be openable and closable so as to make the optical-axis aperture a large diameter or a small diameter, and a quantity of light is thereby adjusted.
For example, Patent Document 1 [Japanese Patent Application Publication No. 2009-20438 (FIG. 1, FIG. 4)] discloses an iris diaphragm apparatus in which a plurality of blades is disposed around an optical-axis aperture formed in a substrate, and opens and closes the light path diameter from a small diameter to a large diameter in similar shapes. It is known that such a diaphragm apparatus has the feature of adjusting a quantity of light in multi-stage with diameters close to a circular shape using a plurality of blades.
The Document discloses an open/close mechanism in which a plurality of diaphragm blades is disposed between a pair of upper and lower ring-shaped substrates having a light-path aperture at the center, and is opened and closed by a driving unit provided in one of the substrates.
Further, Patent Document 2 [Japanese Patent Application Publication No. 2006-322979 (FIG. 1)] discloses an apparatus in which a plurality of diaphragm blades is disposed between substrates formed in the shape of a ring as in Document 1, and is opened and closed by a driving unit provided in one of the substrates. Such an apparatus is known well that a plurality of blades is disposed around the light-path aperture in the shape of scales, and is opened and closed by a driving unit provided in one of the substrates.
Then, in a mechanism for opening and closing a plurality of blades, guide grooves are provided in the substrate along the trajectory of motion of the blades, pins planted in the blades are fitted into the guide grooves, the blades are rotated in a predetermined direction by a transmission ring provided in the other substrate, and the motion of the plurality of blades is thereby regulated. In the substrate for supporting the blades, guide grooves corresponding to the number of blades are disposed around the light-path aperture. The structure of the guide grooves is disclosed in FIG. 4 of Patent Document 1.
Further, Patent Document 2 discloses an apparatus for adjusting a quantity of light in the optical-axis aperture of the substrate with two blades. Then, the substrate is provided with an electromagnetic driving unit that opens and closes a plurality of blades, and rotation of the driving unit is to shift rotationally a plurality of blades concurrently by a driving ring in the apparatus of Patent Document 1, and is to shift slidably two blades concurrently by a driving arm in the apparatus of Patent Document 2.
The diaphragm apparatus as described above is already known in Patent Documents 1, 2, etc. in which a plurality of blades is disposed around a light-path aperture, and is opened and closed to adjust the light-path diameter to be larger and smaller. In this case, a plurality of diaphragm blades is supported between a pair of upper and lower substrates formed of a synthetic resin or metal, and the front end portions of the blades face the light-path aperture, while the base end portions thereof are supported in the substrate around the light-path aperture.
Therefore, conventionally, for example, a ring-shaped driving ring is provided in one of the substrates, the driving ring is rotated by a driving unit, and the motion is transmitted to each blade member. Then, in the other substrate, guide holes are provided in the motion direction to accurately open and close the blade front end portions, and are fitted into the pins provided in the blades.
In the blade open/close mechanism with such a structure, a plurality of guide grooves is provided around the light-path aperture in the substrate, and conventionally, the guide holes are configured in the shape of a slit piercing the front and back sides of the substrate and are integrally formed with the substrate.
Meanwhile, the blade members are formed by performing die-cutting forming on a film member (for example, polyethylene film) of a synthetic resin in a predetermined shape, and then, pins are planted in the film members by welding or the like.
The fit state of the guide hole and the planted pin in the conventional blade open/close mechanism will be described with reference to FIGS. 11A to 11C. As shown in FIG. 11A, in a substrate 100, a guide hole 101 is formed by die forming, and a planted pin 102 of a blade 104 is fitted into the guide hole. At this point, the guide hole 101 needs a gap to slide between a cutting taper θ in die forming and the inner diameter of the hole. Due to the taper and gap, the planted pin 102 is sometimes inclined as shown in FIG. 11B. The cause is that the front end of the planted pin comes into point-contact with the inner wall of the guide hole, the blade is inclined by the inclination of the planted pin, and accurate open/close action is not obtained.
Concurrently with this problem, as shown in FIG. 11C, since the guide hole 101 is formed in the shape of a long hole along the trajectory in the open/close direction of the blade, exterior light enters toward a light-path aperture 103 in the direction of the arrow in FIG. 11C. This guide hole is formed in a plurality of portions around the light-path aperture, and therefore, there is the problem that the exterior light enters inside the light path.
Further, in the above-mentioned conventional apparatus, each blade member is directly supported between the first substrate and the driving ring to be openable and closable, and therefore, the following problems occur. Smooth motion of the blade is hindered by frictional resistance occurring between each blade member and the first substrate or between each blade member and the driving ring, and concurrently therewith, power consumption in the driving apparatus is large, resulting in the problem.
Furthermore, static electricity is generated between the first substrate and blade members or between the driving ring and blade members due to open/close action of the blades, and it is known that open/close failure of the blade is caused when the static electricity is charged and accumulated. Conventionally, to prevent static electricity from being accumulated, for example, the substrate is made by forming of resin with conductive metal or conductive fibers such as carbon mixed. However, when fibers are mixed, the fibers are exposed to the substrate surface, and interfere with motion of the blade.
Therefore, the inventor of the invention arrived at the idea of providing guide plates between blades and a substrate and between blades and a driving ring in supporting a plurality of blade members between a pair of upper and lower substrates to be openable and closable, and reducing frictional resistance by the guide plate, while at the same, reducing the occurrence of static electricity.
However, when the inventor produced the blades and guide plates by die-cutting forming of a polyethylene resin film and observed the open/close state of the blades, the following problem newly occurred.
Fit holes are provided in the driving ring and the guide plate provided therein and fitted into protrusions (pins) of the blades, and a plurality of blades is opened and closed by rotation of the driving ring. At this point, due to misalignment of the fit holes of the ring and plate, and accuracy difference of the hole inner diameters, the blade is regulated by the fit hole of the plate to be opened and closed, and is sometime not in conjunction with open/close motion of the driving ring. Also in the case of providing guide grooves to regulate open/close motion of the blades in the substrate and the guide plate provided therein, when misalignment and accuracy error occur between mutual guide grooves, the blades perform unstable open/close motion.
This state is shown in FIGS. 12A to 12C. When a backlash Δt1 occurs between a fit hole 111 of a driving ring 110 and a fit hole 121 of an upper guide plate 120 due to misalignment or dimension accuracy, for example, at the time the driving ring rotates in a clockwise direction to open and close blades 104, as shown in FIG. 12B, some blade rotates faster by Δt1, while another blade rotates slower by Δt1. Then, when the driving ring 110 rotates in a counterclockwise direction, inversely, the blade rotates slower by Δt1, and deviation of the aperture amount occurs in the aperture diameter of the blades. Similarly, in between the substrate 100 and a lower guide plate 105 provided therein, when a guide groove 102 and a guide groove 103 cause a backlash due to misalignment or dimension accuracy, and as shown in FIG. 12C, a backlash Δt2 occurs, the open/close trajectory of the blade deviates by Δt2.
Further, in the above-mentioned conventional apparatus, a plurality of blades is disposed between a pair of upper and lower substrates having light-path apertures to be openable and closable, and the diaphragm apparatus for adjusting the light-path diameter to be larger and smaller by the plurality of blades is already known in Patent Documents 1 and 2, etc. In this case, to concurrently open and close a plurality of diaphragm blades, such an open/close mechanism is known that the driving ring is provided in one of the substrates to be rotatable, and the driving ring and each blade member are coupled by pin-slit connection to drive open and close.
As the conventional open/close mechanism, there known an arm transmission mechanism in which an arm is provided in a place of the driving ring, and is coupled to a transmission lever coupled to a driving source such as an electromagnetic driving apparatus, and a gear transmission mechanism in which a driving gear is provided in the rotary shaft coupled to the driving source, and a tooth form meshing with the driving gear is formed in the driving ring.
In the former arm transmission mechanism, a rotation ring is provided around the light-path aperture, the arm extends from the ring to the outside of the aperture and is coupled to the driving apparatus, and therefore, the problem is known that the apparatus is made a large diameter to the outside of the aperture. Meanwhile, in the latter blade open/close mechanism by gear transmission, the rotation ring provided around the light-path aperture and the driving apparatus are coupled by gear, and therefore, the problem is known that the gear connection portion protrudes to the outside of the ring and that the apparatus is made a large diameter.
Then, in the gear transmission mechanism, attempts are made such that a concave portion (cut) is provided on the light-path center side in part of the outer region of the driving ring, and that the gear coupling portion is disposed inside the concave portion. In such a transmission structure, since the gear coupling portion does not protrude to the outside of the driving ring, it is possible to make the apparatus a small diameter.
FIG. 13 shows the gear transmission mechanism. A blade 101 is supported between a pair of upper and lower substrates 100a, 100b, the driving ring 102 is disposed in one of the substrates to be rotatable, a concave portion 105 is formed by cutting part of the driving ring, a tooth form 108 is formed in the end face of the cut concave portion 105 to mesh with a driving gear 109 of a driving apparatus (not shown), and in this case, the following problem occurs.
As shown in FIG. 13B, the blade sometimes warps and sinks into the cut concave portion 105 formed in the driving ring 102. In other words, the blade 101 is sandwiched and supported between one of the substrates, 100a, and the driving ring 102 to be openable and closable, the cut concave portion 105 is provided in part of the driving ring, and therefore, the blade such that the open/close trajectory is positioned in the cut concave portion may partially warp and sink into the inside of the concave portion. FIG. 13B shows this state. When the base end portion of the blade sinks into the inside of the concave portion, there is the problem that the blade front end floats and interferes with the other blade front end, and in the case of the mechanism for fitting a protrusion 106 of the blade and a guide groove 107 of the substrate as shown in the figure, smooth motion is prevented in the fit portion.
In this case, when the cut concave portion of the driving ring is formed outside the open/close trajectory of the blade, sinking of the blade is avoided, but the driving ring is made a large diameter to the outside of the motion trajectory of the blade, the size of the diaphragm apparatus is increased concurrently with increases in slide friction with the blade, and the problem arises that the barrel of the image pickup apparatus to incorporate the diaphragm apparatus is increased in size.